This invention relates to a magnetic head assembly and, more particularly, to such an assembly which includes a deflectable piezo-electric support member for the magnetic head and which, when energized, is adapted to displace the head.
In various types of signal recording and/or reproducing apparatus, it is advantageous to adjust the magnetic head in its relation to the magnetic medium upon which signals are recorded. For example, in an audio magnetic tape recorder, audio signals generally are recorded in one or more longitudinal tracks on the magnetic tape. Because of various factors, the relationship of the head with respect to a record track during a playback operation may differ from the relationship of the head with respect to the record track during the recording operation. In this instance, the head should be adjustable such that it can be positioned during the playback operation in the same juxtaposition with respect to the record track as was experienced during the recording operation. Also, in video signal recording/reproducing apparatus, such as a video tape recorder (VTR), video signals are recorded in parallel, skewed tracks by rotating magnetic heads, and the position of these heads often must be adjusted during the playback operation so as to coincide with the recorded tracks.
It has been proposed to provide an adjustable support for a magnetic head for use in the aforementioned audio or video apparatus. This adjustable support, known to those of ordinary skill in the art as a bi-morph leaf assembly, is responsive to an electrical voltage so as to deflect, thereby displacing the magnetic head supported thereon. The amount and direction of this deflection, and thus the amount and direction of displacement of the magnetic head, is a function of the amplitude and polarity of the energizing voltage supplied to the bi-morph leaf assembly. Thus, and for the environment of a VTR, in the event that, during a playback operation, the scanning traces of the magnetic heads do not coincide with the record tracks, the bi-morph leaf assemblies can be suitably energized so as to displace the heads, whereby their scanning traces now conform to the previously recorded record tracks. An example of one type of bi-morph leaf assembly is disclosed in copending application Ser. No. 825,861, now U.S. Pat. No. 4,167,763 assigned to the assignee of the present invention. As described therein, the bi-morph leaf assembly is constructed of two leaves of piezo-electric ceramic material, each leaf having its opposite surfaces plated with electrodes, the leaves being in electrical and mechanical contact with each other. Depending upon the voltage applied across the leaves, the piezo-electric ceramic members deflect accordingly. Other examples of bi-morph leaf assemblies are described in U.S. Pat. No. 4,080,636 and U.S. Pat. No. 3,787,616.
One difficulty in assembling and using bi-morph leaf assemblies is in the connection of the electrical conducting lead or leads to the electrically conductive surfaces thereof. Typically, a lead is soldered to the bi-morph leaf assembly. However, this results in heating the assembly, whereby the electrical and/or physical characteristics thereof are deleteriously affected. Furthermore, the soldering process is quite time-consuming and, thus, expensive, and must be performed by a skilled technician. Also, there is difficulty in obtaining unformity in these assembled bi-morph leaf assemblies. Hence, proper quality control often is not achieved.
Another problem encountered with bi-morph leaf assemblies is that of mechanically coupling the assembly to a suitable support structure. For example, in the environment of a VTR, the assembly must be mounted on a rotary device, such as a rotary drum. This can be accomplished by securing the bi-morph leaf assembly to a mounting plate by the use of mounting screws which pass through the assembly into the plate. When so mounted, electrical leads can be soldered to lugs which are secured to the electrically conductive surfaces of the bi-morph assembly. However, for this mounting arrangement, a hole must be provided in the bi-morph assembly for the mounting screw. It may be difficult to provide such a hole and, moreover, may degrade the characteristics of the ceramic material from which the bi-morph assembly is constructed. For example, the strength of the material may be seriously weakened. Also, if this mounting arrangement is to be used in, for example, a rotary head record/playback device, vibrations in the assembly, which may be expected during normal recording or playback operations, may loosen the mounting screw, thereby affecting the stability of the mounting assembly. Still further, the securing of the bi-morph leaf assembly to the mounting plate also is time-consuming.